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                  <p class="p_Heading1"><span class="f_Heading1">Datastore</span></p>



  
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                <p class="p_TextIndentedL2"><img src="d_datastore.png" width="106" height="64" border="0" alt="d_Datastore"></p>
<p class="p_BodyText"><span class="f_BodyText">A </span><span class="f_BodyText" style="font-style: italic;">Datastore</span><span class="f_BodyText"> is an element used to define permanently stored data. A token of data that enters into a Datastore is stored permanently, updating tokens for data that already exists. A token of data that comes out of a Datastore is a copy of the original data.</span></p>
<p class="p_BodyText"><span class="f_BodyText">Use </span><span class="f_BodyText" style="font-style: italic;"><a href="objectflow.htm">Object Flow</a></span><span class="f_BodyText"> connectors to connect elements (such as <a href="activity.htm">Activities</a>) to Datastores, as values and information are being passed between nodes. Selection and transformation behavior, together composing a sort of query, can be specified as to the nature of data access. For instance, selection behavior determines which objects are affected by the connection to the Datastore. Transformation behavior might then further specify the value of an attribute pertaining to a selected object.</span></p>
<p class="p_BodyText"><span class="f_BodyText">To define the behavior of access to a Datastore, attach a note to the </span><span class="f_BodyText" style="font-style: italic;">Object Flow</span><span class="f_BodyText"> connector. To do this, right-click on the Object Flow and select </span><span class="f_MenuKeyField">Attach Note or Constraint</span><span class="f_BodyText">. A dialog indicates other flows in the <a href="activitydiagram.htm">Activity diagram</a>, to which you can attach the note (if the behavior applies to multiple flows). To comply with UML 2, preface behavior with the notation &laquo;</span><span class="f_BodyText" style="font-style: italic;">selection</span><span class="f_BodyText">&raquo; or &laquo;</span><span class="f_BodyText" style="font-style: italic;">transformation</span><span class="f_BodyText">&raquo;.</span></p>
<p class="p_SubHeadingL1"><span class="f_SubHeadingL1">Toolbox Icon</span></p>
<p class="p_TextIndentedL2"><img src="e_datastore.png" width="171" height="22" border="0" alt="e_Datastore"></p>
<p class="p_SubHeadingL1"><span class="f_SubHeadingL1">OMG UML Specification</span></p>
<p class="p_BodyText"><span class="f_BodyText">The OMG UML specification (</span><span class="f_BodyText" style="font-style: italic;">UML Superstructure Specification, v2.1.1, p. 360</span><span class="f_BodyText">) states:</span></p>
<p class="p_OMGText"><span class="f_OMGText">A data store node is a central buffer node for non-transient information... A data store keeps all tokens that enter it, copying them when they are chosen to move downstream. Incoming tokens containing a particular object replace any tokens in the object node containing that object.</span></p>




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